This invention relates to a novel brazing filler metal composition. The present invention is particularly concerned with a brazing material suitable for joining copper and copper alloys.
For years the phosphorous-copper alloys, also known as phos-coppers, have proven to be excellent brazing filler metals for joining copper and copper alloys in a variety of applications. Through the years a number of metallic elements have been added to impart useful, special properties to the basic phos-coppers. Among these elements have been silver, tin, nickel and antimony. Most all have been added with the intent of lowering the melting range or, to allow lower phosphorous contents thereby improving ductility.
In the past researchers have disclosed the addition of many elements to the phos-coppers but none with the novel combination of tin and antimony resulting in a brazing filler metal with the improved properties disclosed herein. The composition of the present invention is not disclosed or suggested by any prior art.
Vaders, in U.S. Pat. No. 2,069,906 discloses the addition of phosphorous and antimony to copper for a welding electrode wherein the phosphorus is present in very small amounts as a deoxidizing agent. This combination melts at a very high temperature and is entirely unsuitable for brazing.
Smith, in his U.S. Pat. No. 2,073,077 suggests that high tin contents when added in combination with phosphorous lower the melting range of the filler metal. He mentions small amounts of antimony only as an impurity. Smith claims a tin content of 13-15% and phosphorous from 3.5-5.5%. The resulting alloys are quite brittle and according to Smith are available in cast or granulated forms only. These alloys are too brittle and are not suitable for most brazing applications.
Kalischer, in his U.S. Pat. No. 2,161,057, covers the addition of antimonv onlv to the phos-coppers and indicates various "flow points" for various combinations of antimony and phosphorus, but does not indicate solidus and liquidus temperatures. The actual melting ranges of these alloys vary widely and do no reflect the advantages attributable to the combination of tin and antimony.
Accordingly, the object of the present invention is to provide a brazing filling metal having the desirable ductility and melting range. Another object of the present invention is to provide a phosphorous copper based alloy which has improved joint appearance. Still a further object of the invention is to produce a phosphorous copper alloy for brazing which reduces braze residue and which is susceptible to easy cleaning. Yet another object of this invention is to provide a low-cost phosphorous copper alloy for brazing which is capable of filling poorly fitting joints.